System and method for applying high temperature corrosion resistant amorphous based coatings

ABSTRACT

An embodiment relates to a material comprising a ceramic formed from an amorphous metal alloy (amorphous metal ceramic composite), wherein the composite exhibits a higher corrosion resistance than that of Haynes 230 when exposed to molten chlorides such as KCl or MgCl2 or combinations thereof at temperatures up to 750° C. Yet, another embodiment relates to a method comprising obtaining a substrate, forming a coating of an amorphous metal alloy, heating the coating, and transforming at least a portion the amorphous metal alloy into an amorphous metalceramic composite.

FIELD OF THE INVENTION

This invention relates to the application of amorphous based coatings toprevent corrosion against molten salt on applied surfaces; moreparticularly, amorphous based coatings compositions are disclosed, whereapplication of the coating to a material provides corrosion resistanceagainst molten salt in a superior fashion to the products currently usedto prevent corrosion resistance against molten salt.

BACKGROUND OF INVENTION

Compared to metallic alloy materials with a crystalline microstructure,“[i]t is widely known that metallic glasses are solid alloys [that][exhibit] many superior properties”, where “[t]he unique properties [ofmetallic glasses] originate from [their] random atomic arrangement . . .that contrasts with the regular atomic lattice arrangement found incrystalline alloys.” [Source: “Classification of Bulk Metallic Glassesby Atomic Size Difference, Heat of Mixing and Period of ConstituentElements and Its Application to Characterization of the Main AlloyingElement”; Takeuchi, A.; Inoue, A.; Materials Transactions, Vol. 46, No.12 (2005) pp. 2817 to 2829].

“The mechanical properties of amorphous alloys have proven bothscientifically unique and of potential practical interest, although theunderlying deformation physics of these materials remain less firmlyestablished as compared with crystalline alloys.” [Source: Mechanicalbehavior of amorphous alloys”; Schuh, C.; Hufnagel, T.; Ramamurty, U.;Acta Materialia 55 (2007) 4067 4109]. Further, “[t]he mechanics ofmetallic glasses have proven to be of fundamental scientific interestfor their contrast with conventional crystalline metals, and also occupya unique niche compared with other classes of engineering materials. Forexample, amorphous alloys generally exhibit elastic moduli on the sameorder as conventional engineering metals . . . but have room-temperaturestrengths significantly in excess of those of polycrystals withcomparable composition. The consequent promise of high strength withnon-negligible toughness has inspired substantial research effort on theroom-temperature properties of metallic glasses.” [Source: Mechanicalbehavior of amorphous alloys”; Schuh, C.; Hufnagel, T.; Ramamurty, U.;Acta Materialia 55 (2007) 4067 4109].

One of the areas in which much research has been conducted is in theability of amorphous alloys to demonstrate corrosion resistance. “Anumber of amorphous metals exhibit excellent corrosion resistance, whichhas been explained in terms of their structural homogeneity. Sinceamorphous metals are in principle structurally and chemicallyhomogeneous and thus lack any microstructure, such as grain boundaries,which could act as local electrochemically-active sites, manyresearchers attribute good corrosion resistance to the entire class ofamorphous metals.” [Schroeder, Valeska et al. “Comparison of thecorrosion behavior of a bulk amorphous metal,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni₁₀Be_(22.5), with its crystallized form.”(1998).]. It is established that amorphous metals have good corrosionresistance, and their properties have been called upon for use in manyapplications which require corrosion resistance.

Corrosion resistance is required in many industries. Specifically, thereis a need for corrosion resistance against molten salt. Industries whichrequire protection against corrosion resulting from molten salt exposureinclude the power industry, desalination industry, chemical, oil andgas, power generation industry, and aerospace industry. In the powerindustry, corrosion resistance against molten salts is needed forconcentrated solar power, molten salt batteries, and thermal batteriesused extensively in military applications, especially for guidedmissiles, as a power source. In desalination, the resistance is neededfor pumps, compressors, heat exchangers, and valves. For the chemicalindustry, corrosion restrained against molten salts is required fornozzles, castings, valves, and pumps. In the oil and gas industry,resistance against molten salt is needed for impellers, centralizers,and inserts. In the power generation industry, resistance against moltensalt corrosion is needed for heat shields, boiler tubes, seals, andshields. Lastly, in the aerospace industry, corrosion resistance againstmolten salts is needed for turbine blades, compressors, nozzles, gears,and chambers. Current products available in the market do not providefull protection against corrosion due to molten salt exposure and have alackluster performance. One of the premier products currently available,the Haynes 230 alloy, still allows for a corrosion of 0.67 millimetersper year. Current products available on the market offer only lacklusterperformance.

The ultimate tensile strength of all Ni-based alloys reduces rapidlyafter 600° C. Cho et al. studied and modelled the corrosion resistanceof Fe—Ni—Cr alloy under KCl—MgCl₂ at a temperature range of 700° C. to1,000° C. The experiment results and the model predictions showed thatthe selective Cr corrosion is mass transfer driven and the depletioncould be further increased in CSP systems with forced convection.Several coatings including iron- and nickel-based alloys, nickelelectroplating, molybdenum thermal spray, and diamond like coatings andpost-processing techniques were investigated at University ofWisconsin-Madison. They showed that Ni-electroplated coatings were themost promising, while Mo thermal spray and diamond like carbon coatingshad spalling issues. The Ni-plating was shown to greatly reduce the rateof corrosion due to chromium dealloying from the base alloy.

In “High-efficiency concentrated solar power plants need appropriatematerials for high-temperature heat capture, conveying and storage”published in Energy, Volume 139, 15 Nov. 2017, Pages 52-64, Zhang et al.state: “Temperatures of 600-900° C. foster the use of high-efficiencypower generation cycles.” Researchers are looking for high temperaturecorrosion resistant coatings because at above 600° C. the efficiency ofconcentrated solar power plants are high and the electricity costs($/kWh) are drastically reduced.

To operate concentrated solar power plants at above 700° C., theconcentrated solar power plants need to use molten salts like chloridesalts for both heat transfer and thermal energy storage. Currently, theconcentrated solar power plants use nickel-based alloys, which areextremely expensive. Typically, the nickel-based alloy are Haynesalloys, which too are not able to provide the corrosion resistance of 15micrometer/year or less at above 700° C.

Accordingly, it would be desirable to develop an amorphous metal coatinghaving a unique composition such that the amorphous metal is capable ofproviding full corrosion resistance to a material it is coated toagainst molten salts. This would improve the performance of manyindustries in which molten salts are used.

An embodiment relates to a material comprising a composite comprising anamorphous metal ceramic composite formed from an amorphous metal alloy,wherein the composite exhibits a higher corrosion resistance than thatof Haynes 230 when exposed to molten KCl or MgCl₂ or combinationsthereof at a temperature up to 750° C.

In an embodiment, the composite exhibits no corrosion when exposed tothe molten KCl or MgCl₂ or combinations thereof at the temperature up to750° C.

In an embodiment, the composite is formed from the amorphous metal alloywithin 300 hours by exposing the amorphous metal alloy to a temperatureabove 650° C. In an embodiment, the composite is not fully amorphous orat least partially crystalline. In an embodiment, the compositecomprises a boride and a carbide. In an embodiment, the material isconfigured to be a component of a solar concentrator. In an embodiment,the composite exhibits substantially no corrosion when exposed to themolten KCl or MgCl₂ for at least 30 years. In an embodiment, theamorphous metal alloy is partially or fully amorphous. In an embodiment,the amorphous metal alloy comprises a nickel based alloy and/or an ironbased alloy. In an embodiment, the composite comprises a coating.

Another embodiment relates to a method comprising obtaining a substrate,forming a coating of an amorphous metal alloy, heating the coating, andtransforming at least a portion the amorphous metal alloy into acomposite comprising an amorphous metal ceramic composite. In anembodiment, the forming the coating comprises thermally and/ornon-thermally spraying the amorphous metal alloy.

In an embodiment, the composite exhibits a higher corrosion resistancethan that of Haynes 230 when exposed to molten KCl or MgCl₂ orcombinations thereof at a temperature at 750° C. for a period of 300hours. In an embodiment, the composite exhibits no corrosion whenexposed to molten KCl or MgCl₂ or combinations thereof at a temperatureat 750° C. for a period of at least 300 hours. In an embodiment, thecomposite is formed from the amorphous metal alloy within 300 hours byexposing the amorphous metal alloy to a temperature above 600° C. In anembodiment, the composite is not fully amorphous or at least partiallycrystalline. In an embodiment, the composite comprises a boride and acarbide. In an embodiment, the composite exhibits substantially nocorrosion when exposed to the molten KCl or MgCl₂ or combinationsthereof at a temperature up to 750° C. for at least 30 years. In anembodiment, the amorphous metal alloy is partially or fully amorphous.In an embodiment, the amorphous metal alloy comprises a nickel basedalloy and/or an iron based alloy. An embodiment relates to a compositioncomprising an amorphous nickel-based alloy.

Additional embodiments relates to a composition, wherein the amorphousalloy comprises Ni, Fe, Cr, X, and Y, wherein: X and Y are elements, andX is selected from the group consisting molybdenum, copper, cobalt,aluminum, titanium, tungsten, niobium, silicon, vanadium, andcombinations thereof, and the Y is selected from the group consisting ofboron, carbon, silicon, and combinations thereof. The composition, wherethe amorphous alloy comprises Ni_(100-(a+b+c+d))(Cr_(a)X_(b)Y_(c)),wherein: a is in the range of 10 to 50 wt %; b is under 30 wt %, and cis in the range of 0 to 10 wt %. The composition, where the amorphousalloy comprises Ni_(100-(a+b+c+d))(Cr_(a)X_(b)Y_(c)), wherein: a is inthe range of 10 to 50 wt %; b is in the range of 10-30 wt %, and c is inthe range of 0 to 10 wt %. The composition, wherein the amorphous alloycomprises Fe_(100-(a+b+c+d))(Cr_(a)X_(b)Y_(c)), wherein: a is in therange of 15 to 40 wt. %; b is in the range of 10 to 30 wt. % and c isunder 10 wt %.

Additional embodiments relates to a method comprising depositing amolten amorphous feedstock to form a first amorphous layer comprising acomposition, wherein the molten amorphous feedstock comprises:

Ni_(100(a+b+c+d))(Cr_(a)X_(b)Y_(c)), wherein: a is in the range of 10 to50 wt %; b is under 30 wt %, and c is in the range of 0 to 10 wt %. orNi_(100(a+b+c+d))(Cr_(a)X_(b)Y_(c)), wherein: a is in the range of 10 to50 wt %; b is in the range of 10 to 30 wt %, and c is in the range of 0to 10 wt %.

or Fe_(100(a+b+c+d))(Cr_(a)X_(b)Y_(c)), wherein: a is in the range of 15to 40 wt. %; b is in the range of 10 to 30 wt. % and c is under 10 wt %.The method, wherein the depositing the molten amorphous feedstockcomprises thermal spray coating, which encompasses high velocity oxygenfuel, plasma spraying, and/or arc spraying. The method, wherein thefirst amorphous layer and the second amorphous layer are deposited on asubstrate wherein an outermost surface layer of the substrate isphase-transformed such that the outermost surface layer comprises anamorphous material and at least a portion of the substrate comprises apartially crystalline material or a fully crystalline material beneaththe outermost surface layer.

Another embodiment relates to a method comprising: metallic, ceramic,cermet, and some polymeric materials in the form of powder, wire, or rodare fed to a torch or gun with which they are heated to near or somewhatabove their melting point. The resulting molten or nearly moltendroplets of material are accelerated in a gas stream and projectedagainst the surface to be coated.

BRIEF DESCRIPTION OF THE FIGURES

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 shows a schematic Time-Temperature-Transformation (TTT) diagramthat shows crystallization kinetics amorphous metals vs. crystallinemetals.

FIG. 2 shows an Ashby map of the damage tolerance (toughness vs.strength) for different materials (Nature Materials 10, 123-128, (2011).

FIG. 3 Shows the cross-sectional micrographs of coated and uncoatedAlloy 230 exposed to KCl—MgCl₂ for 300 hours at 750° C.

FIG. 4 Cross-section optical micrographs of uncoated Haynes 230 exposedto KCl—MgCl₂ for 300 hours at 750° C.

FIG. 5 shows the SEM-EDS mapping of uncoated Haynes 230 exposed toKCl—MgCl₂ for 300 hours at 750° C.

FIG. 6 shows the SEM-EDS mapping of Haynes 230 with Ni-3 coating exposedto KCl—MgCl₂ for 300 hours at 750° C.

FIG. 7 shows box and whisker plots showing depth of attack on theuncoated samples. The coated samples exhibited no attack on the basemetal.

DETAILED DESCRIPTION Definitions and General Techniques

All publications, patents, and patent applications cited in thisSpecification are hereby incorporated by reference in their entirety.The singular forms “a,” “an” and “the” are used herein to refer to oneor to more than one (i.e., to at least one) of the grammatical object ofthe article. By way of example, “a polymer resin” means one polymerresin or more than one polymer resin. Any ranges cited herein areinclusive. The terms “substantially” and “about” used throughout thisSpecification are used to describe and account for small fluctuations.For example, they can refer to less than or equal to ±5%, such as lessthan or equal to ±2%, such as less than or equal to ±1%, such as lessthan or equal to ±0.5%, such as less than or equal to ±0.2%, such asless than or equal to ±0.1%, such as less than or equal to ±0.05%.

Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”), area recently developed class of metallic materials. These alloys may besolidified and cooled at relatively slow rates, and they retain theamorphous, non-crystalline (i.e., glassy) state at room temperature.Amorphous alloys have many superior properties, e.g., physicalproperties, than their crystalline counterparts. However, if the coolingrate is not sufficiently high, crystals may form inside the alloy duringcooling, so that the unique benefits of the amorphous state can be lost.For example, one challenge with the fabrication of bulk amorphous alloyparts is the partial crystallization of parts due to either slow coolingor impurities prevalent in the raw alloy material. As a high degree ofamorphicity (and, conversely, a low degree of crystallinity) isdesirable in BMG parts, there is a need to develop methods for castingBMG parts having predictable and controlled amount of amorphicity.

FIG. 1 (obtained from U.S. Pat. No. 7,575,040) shows aviscosity-temperature graph of a bulk solidifying amorphous alloy, fromthe VIT-001 series of Zr—Ti—Ni—Cu—Be family manufactured by LiquidmetalTechnology. It should be noted that there is no clear liquid/solidtransformation for a bulk solidifying amorphous metal during theformation of an amorphous solid. The molten alloy becomes more and moreviscous with increasing undercooling until it approaches solid formaround the glass transition temperature. Accordingly, the temperature ofsolidification front for bulk solidifying amorphous alloys can be aroundglass transition temperature, where the alloy will practically act as asolid for the purposes of pulling out the quenched amorphous sheetproduct.

FIG. 2 (obtained from U.S. Pat. No. 7,575,040) shows atime-temperature-transformation (TTT) cooling curve 200 of a bulksolidifying amorphous alloy, or TTT diagram. Bulk-solidifying amorphousmetals do not experience a liquid/solid crystallization transformationupon cooling, as with conventional metals. Instead, the highly fluid,non-crystalline form of the metal found at high temperatures (near a“melting temperature” Tm) becomes more viscous as the temperature isreduced (near to the glass transition temperature Tg), eventually takingon the outward physical properties of a conventional solid. Even thoughthere is no liquid/crystallization transformation for a bulk solidifyingamorphous metal, a “melting temperature” Tm may be defined as thethermodynamic liquidus temperature of the corresponding crystallinephase. Under this regime, the viscosity of bulk-solidifying amorphousalloys at the melting temperature could lie in the range of about 0.1poise to about 10,000 poise, and even sometimes under 0.01 poise. Alower viscosity at the “melting temperature” would provide faster andcomplete filling of intricate portions of the shell/mold with a bulksolidifying amorphous metal for forming the BMG parts. Furthermore, thecooling rate of the molten metal to form a BMG part has to be such thatthe time-temperature profile during cooling does not traverse throughthe nose-shaped region bounding the crystallized region in the TTTdiagram of FIG. 2 . In FIG. 2 , T_(nose) is the critical crystallizationtemperature Tx where crystallization is most rapid and occurs in theshortest time scale.

The supercooled liquid region, the temperature region between Tg and Txis a manifestation of the extraordinary stability againstcrystallization of bulk solidification alloys. In this temperatureregion the bulk solidifying alloy can exist as a high viscous liquid.The viscosity of the bulk solidifying alloy in the supercooled liquidregion can vary between 1012 Pa s at the glass transition temperaturedown to 105 Pa s at the crystallization temperature, the hightemperature limit of the supercooled liquid region. Liquids with suchviscosities can undergo substantial plastic strain under an appliedpressure. The embodiments herein make use of the large plasticformability in the supercooled liquid region as a forming and separatingmethod.

One needs to clarify something about Tx. Technically, the nose-shapedcurve shown in the TTT diagram describes Tx as a function of temperatureand time. Thus, regardless of the trajectory that one takes whileheating or cooling a metal alloy, when one hits the TTT curve, one hasreached Tx. In FIG. 2 , Tx is shown as a dashed line as Tx can vary fromclose to Tm to close to Tg.

The schematic TTT diagram of FIG. 2 shows processing methods of diecasting from at or above Tm to below Tg without the time-temperaturetrajectory (shown as (1) as an example trajectory) hitting the TTTcurve. During die casting, the forming takes place substantiallysimultaneously with fast cooling to avoid the trajectory hitting the TTTcurve. The processing methods for superplastic forming (SPF) from at orbelow Tg to below Tm without the time-temperature trajectory (shown as(2), (3) and (4) as example trajectories) hitting the TTT curve. In SPF,the amorphous BMG is reheated into the supercooled liquid region wherethe available processing window could be much larger than die casting,resulting in better controllability of the process. The SPF process doesnot require fast cooling to avoid crystallization during cooling. Also,as shown by example trajectories (2), (3) and (4), the SPF can becarried out with the highest temperature during SPF being above T_(nose)or below T_(nose), up to about Tm. If one heats up a piece of amorphousalloy but manages to avoid hitting the TTT curve, you have heated“between Tg and Tm”, but one would have not reached Tx.

Typical differential scanning calorimeter (DSC) heating curves ofbulk-solidifying amorphous alloys taken at a heating rate of 20 C/mindescribe, for the most part, a particular trajectory across the TTT datawhere one would likely see a T_(g) at a certain temperature, a T_(x)when the DSC heating ramp crosses the TTT crystallization onset, andeventually melting peaks when the same trajectory crosses thetemperature range for melting. If one heats a bulk-solidifying amorphousalloy at a rapid heating rate as shown by the ramp up portion oftrajectories (2), (3) and (4) in FIG. 2 , then one could avoid the TTTcurve entirely, and the DSC data would show a glass transition but no Txupon heating. Another way to think about it is trajectories (2), (3) and(4) can fall anywhere in temperature between the nose of the TTT curve(and even above it) and the Tg line, as long as it does not hit thecrystallization curve. That just means that the horizontal plateau intrajectories might get much shorter as one increases the processingtemperature.

Phase

The term “phase” herein can refer to one that can be found in athermodynamic phase diagram. A phase is a region of space (e.g., athermodynamic system) throughout which all physical properties of amaterial are essentially uniform. Examples of physical propertiesinclude density, index of refraction, chemical composition and latticeperiodicity. A simple description of a phase is a region of materialthat is chemically uniform, physically distinct, and/or mechanicallyseparable. For example, in a system consisting of ice and water in aglass jar, the ice cubes are one phase, the water is a second phase, andthe humid air over the water is a third phase. The glass of the jar isanother separate phase. A phase can refer to a solid solution, which canbe a binary, tertiary, quaternary, or more, solution, or a compound,such as an intermetallic compound. As another example, an amorphousphase is distinct from a crystalline phase.

Metal, Transition Metal, and Non Metal

The term “metal” refers to an electropositive chemical element. The term“element” in this Specification refers generally to an element that canbe found in a Periodic Table. Physically, a metal atom in the groundstate contains a partially filled band with an empty state close to anoccupied state. The term “transition metal” is any of the metallicelements within Groups 3 to 12 in the Periodic Table that have anincomplete inner electron shell and that serve as transitional linksbetween the most and the least electropositive in a series of elements.Transition metals are characterized by multiple valences, coloredcompounds, and the ability to form stable complex ions. The term“nonmetal” refers to a chemical element that does not have the capacityto lose electrons and form a positive ion.

Depending on the application, any suitable nonmetal elements, or theircombinations, can be used. The alloy (or “alloy composition”) cancomprise multiple nonmetal elements, such as at least two, at leastthree, at least four, or more, nonmetal elements. A nonmetal element canbe any element that is found in Groups 13-17 in the Periodic Table. Forexample, a nonmetal element can be any one of F, Cl, Br, I, At, O, S,Se, Te, Po, N, P, As, Sb, C, Si, Ge, and B. Occasionally, a nonmetalelement can also refer to certain metalloids (e.g., B, Si, Ge, As, Sb,Te, and Po) in Groups 13-17. In one embodiment, the nonmetal elementscan include B, Si, C, P, or combinations thereof. Accordingly, forexample, the alloy can comprise a boride, a carbide, or both.

A transition metal element can be any of scandium, titanium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium,zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium,osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium,seaborgium, bohrium, hassium, meitnerium, ununnilium, unununium, andununbium. In one embodiment, a BMG containing a transition metal elementcan have at least one of Sc, Y, La, Ac, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd,and Hg. Depending on the application, any suitable transitional metalelements, or their combinations, can be used. The alloy composition cancomprise multiple transitional metal elements, such as at least two, atleast three, at least four, or more, transitional metal elements.

The presently described alloy or alloy “sample” or “specimen” alloy canhave any shape or size. For example, the alloy can have a shape of aparticulate, which can have a shape such as spherical, ellipsoid,wire-like, rod-like, sheet-like, flake-like, or an irregular shape. Theparticulate can have any size. For example, it can have an averagediameter of between about 1 micron and about 100 microns, such asbetween about 5 microns and about 80 microns, such as between about 10microns and about 60 microns, such as between about 15 microns and about50 microns, such as between about 15 microns and about 45 microns, suchas between about 20 microns and about 40 microns, such as between about25 microns and about 35 microns. For example, in one embodiment, theaverage diameter of the particulate is between about 25 microns andabout 44 microns. In some embodiments, smaller particulates, such asthose in the nanometer range, or larger particulates, such as thosebigger than 100 microns, can be used. The alloy sample or specimen canalso be of a much larger dimension. For example, it can be a bulkstructural component, such as an ingot, housing/casing of an electronicdevice or even a portion of a structural component that has dimensionsin the millimeter, centimeter, or meter range.

Solid Solution

The term “solid solution” refers to a solid form of a solution. The term“solution” refers to a mixture of two or more substances, which may besolids, liquids, gases, or a combination of these. The mixture can behomogeneous or heterogeneous. The term “mixture” is a composition of twoor more substances that are combined with each other and are generallycapable of being separated. Generally, the two or more substances arenot chemically combined with each other.

Alloy

In some embodiments, the alloy composition described herein can be fullyalloyed. In one embodiment, an “alloy” refers to a homogeneous mixtureor solid solution of two or more metals, the atoms of one replacing oroccupying interstitial positions between the atoms of the other; forexample, brass is an alloy of zinc and copper. An alloy, in contrast toa composite, can refer to a partial or complete solid solution of one ormore elements in a metal matrix, such as one or more compounds in ametallic matrix. The term alloy herein can refer to both a completesolid solution alloy that can give single solid phase microstructure anda partial solution that can give two or more phases. An alloycomposition described herein can refer to one comprising an alloy or onecomprising an alloy-containing composite. Thus, a fully alloyed alloycan have a homogenous distribution of the constituents, be it a solidsolution phase, a compound phase, or both. The term “fully alloyed” usedherein can account for minor variations within the error tolerance. Forexample, it can refer to at least 90% alloyed, such as at least 95%alloyed, such as at least 99% alloyed, such as at least 99.5% alloyed,such as at least 99.9% alloyed. The percentage herein can refer toeither volume percent or weight percentage, depending on the context.These percentages can be balanced by impurities, which can be in termsof composition or phases that are not a part of the alloy.

Amorphous or Non-Crystalline Solid

An “amorphous” or “non-crystalline solid” is a solid that lacks latticeperiodicity, which is characteristic of a crystal. As used herein, an“amorphous solid” includes “glass” which is an amorphous solid thatsoftens and transforms into a liquid-like state upon heating through theglass transition. Generally, amorphous materials lack the long-rangeorder characteristic of a crystal, though they can possess someshort-range order at the atomic length scale due to the nature ofchemical bonding. The distinction between amorphous solids andcrystalline solids can be made based on lattice periodicity asdetermined by structural characterization techniques such as x-raydiffraction and transmission electron microscopy.

The terms “order” and “disorder” designate the presence or absence ofsome symmetry or correlation in a many-particle system. The terms“long-range order” and “short-range order” distinguish order inmaterials based on length scales.

The strictest form of order in a solid is lattice periodicity: a certainpattern (the arrangement of atoms in a unit cell) is repeated again andagain to form a translationally invariant tiling of space. This is thedefining property of a crystal. Possible symmetries have been classifiedin 14 Bravais lattices and 230 space groups.

Lattice periodicity implies long-range order. If only one unit cell isknown, then by virtue of the translational symmetry it is possible toaccurately predict all atomic positions at arbitrary distances. Theconverse is generally true, except, for example, in quasi-crystals thathave perfectly deterministic tilings but do not possess latticeperiodicity.

Long-range order characterizes physical systems in which remote portionsof the same sample exhibit correlated behavior. This can be expressed asa correlation function, namely the spin-spin correlation function:

In the above function, s is the spin quantum number and x is thedistance function within the particular system. This function is equalto unity when x=x′ and decreases as the distance |x−x′| increases.Typically, it decays exponentially to zero at large distances, and thesystem is considered to be disordered. If, however, the correlationfunction decays to a constant value at large |x−x′|, then the system canbe said to possess long-range order. If it decays to zero as a power ofthe distance, then it can be called quasi-long-range order. Note thatwhat constitutes a large value of |x−x′| is relative.

A system can be said to present quenched disorder when some parametersdefining its behavior are random variables that do not evolve with time(i.e., they are quenched or frozen)—e.g., spin glasses. It is oppositeto annealed disorder, where the random variables are allowed to evolvethemselves. Embodiments herein include systems comprising quencheddisorder.

The alloy described herein can be crystalline, partially crystalline,amorphous, or substantially amorphous. For example, the alloysample/specimen can include at least some crystallinity, withgrains/crystals having sizes in the nanometer and/or micrometer ranges.Alternatively, the alloy can be substantially amorphous, such as fullyamorphous. In one embodiment, the alloy composition is at leastsubstantially not amorphous, such as being substantially crystalline,such as being entirely crystalline.

In one embodiment, the presence of a crystal or a plurality of crystalsin an otherwise amorphous alloy can be construed as a “crystallinephase” therein. The degree of crystallinity (or “crystallinity” forshort in some embodiments) of an alloy can refer to the amount of thecrystalline phase present in the alloy. The degree can refer to, forexample, a fraction of crystals presents in the alloy. The fraction canrefer to volume fraction or weight fraction, depending on the context. Ameasure of how “amorphous” an amorphous alloy is can be amorphicity.Amorphicity can be measured in terms of a degree of crystallinity. Forexample, in one embodiment, an alloy having a low° of crystallinity canbe said to have a high degree of amorphicity. In one embodiment, forexample, an alloy having 60 vol % crystalline phase can have a 40 vol %amorphous phase.

Amorphous Alloy or Amorphous Metal

An “amorphous alloy” is an alloy having an amorphous content of morethan 50% by volume, preferably more than 90% by volume of amorphouscontent, more preferably more than 95% by volume of amorphous content,and most preferably more than 99% to almost 100% by volume of amorphouscontent. Note that, as described above, an alloy high in amorphicity isequivalently low in degree of crystallinity. An “amorphous metal” is anamorphous metal material with a disordered atomic-scale structure. Incontrast to most metals, which are crystalline and therefore have ahighly ordered arrangement of atoms, amorphous alloys arenon-crystalline. Materials in which such a disordered structure isproduced directly from the liquid state during cooling are sometimesreferred to as “glasses.” Accordingly, amorphous metals are commonlyreferred to as “metallic glasses” or “glassy metals.” In one embodiment,a bulk metallic glass (“BMG”) can refer to an alloy, of which themicrostructure is at least partially amorphous. However, there areseveral ways besides extremely rapid cooling to produce amorphousmetals, including physical vapor deposition, solid-state reaction, ionirradiation, melt spinning, and mechanical alloying. Amorphous alloyscan be a single class of materials, regardless of how they are prepared.

Amorphous metals are a new class of materials that have a disordered,non-crystalline, glassy structure, which are created when metals ortheir alloys bypass nucleation and growth of crystalline phases duringsolidification either by cooling very quickly or because of a uniquealloy composition. FIG. 1 (obtained from Nature Materials 10, 123-128,(2011)) shows the time-temperature-transformation (TTT) solidifyingdiagram of an exemplary amorphous and a crystalline alloy. The C shapeof crystalline materials in TTT diagram is the result of the competitionbetween the increasing driving force for crystallization and the slowingof kinetics (effective diffusivity) of the atoms. Both thermodynamic andkinetic parameters affect the crystallization and shift the C shapeposition to larger times.

The position of the nose determines the critical cooling rate to avoidnucleation and crystal growth during cooling and defines the conditionsto manufacture amorphous alloys. In case of amorphous alloys instead ofliquid/solid crystallization transformation, the molten material becomesmore viscous as the temperature reduces near to the glass transformationtemperature and transforms to a solid state after this temperature. Inthe liquid state, the atoms vibrate around positions and have nolong-range ordering. Hence, the critical cooling rate is determined byatomic fluctuations, controlled by thermodynamic factor, rather thankinetic factor. Due to the crystallization bypass, the amorphous alloysremain the most prominent characteristics of the liquids, the absence oftypical long-range ordered pattern of the atomic structure ofcrystalline alloys and any defects associated with it. This disordered,dense atomic arrangement determines the unique structural and functionalproperties of amorphous alloys.

Amorphous metals can be produced through a variety of quick-coolingmethods. For instance, amorphous metals can be produced by sputteringmolten metal onto a spinning metal disk. The rapid cooling, on the orderof millions of degree a second, can be too fast for crystals to form,and the material is thus “locked in” a glassy state. Also, amorphousmetals/alloys can be produced with critical cooling rates low enough toallow formation of amorphous structures in thick layers—e.g., bulkmetallic glasses.

The terms “bulk metallic glass” (“BMG”), bulk amorphous alloy (“BAA”),and bulk solidifying amorphous alloy are used interchangeably herein.They refer to amorphous alloys having the smallest dimension at least inthe millimeter range. For example, the dimension can be at least about0.5 mm, such as at least about 1 mm, such as at least about 2 mm, suchas at least about 4 mm, such as at least about 5 mm, such as at leastabout 6 mm, such as at least about 8 mm, such as at least about 10 mm,such as at least about 12 mm. Depending on the geometry, the dimensioncan refer to the diameter, radius, thickness, width, length, etc. A BMGcan also be a metallic glass having at least one dimension in thecentimeter range, such as at least about 1.0 cm, such as at least about2.0 cm, such as at least about 5.0 cm, such as at least about 10.0 cm.In some embodiments, a BMG can have at least one dimension at least inthe meter range. A BMG can take any of the shapes or forms describedabove, as related to a metallic glass. Accordingly, a BMG describedherein in some embodiments can be different from a thin film made by aconventional deposition technique in one important aspect—the former canbe of a much larger dimension than the latter.

Amorphous metals can be an alloy rather than a pure metal. The alloysmay contain atoms of significantly different sizes, leading to low freevolume (and therefore having viscosity up to orders of magnitude higherthan other metals and alloys) in a molten state. The viscosity preventsthe atoms from moving enough to form an ordered lattice. The materialstructure may result in low shrinkage during cooling and resistance toplastic deformation. The absence of grain boundaries, the weak spots ofcrystalline materials in some cases, may, for example, lead to betterresistance to wear and corrosion. In one embodiment, amorphous metals,while technically glasses, may also be much tougher and less brittlethan oxide glasses and ceramics.

Thermal conductivity of amorphous materials may be lower than that oftheir crystalline counterparts. To achieve formation of an amorphousstructure even during slower cooling, the alloy may be made of three ormore components, leading to complex crystal units with higher potentialenergy and lower probability of formation. The formation of amorphousalloy can depend on several factors: the composition of the componentsof the alloy; the atomic radius of the components (preferably with asignificant difference of over 12% to achieve high packing density andlow free volume); and the negative heat of mixing the combination ofcomponents, inhibiting crystal nucleation and prolonging the time themolten metal stays in a supercooled state. However, as the formation ofan amorphous alloy is based on many different variables, it can bedifficult to make a prior determination of whether an alloy compositionwould form an amorphous alloy.

Amorphous alloys, for example, of boron, silicon, phosphorus, and otherglass formers with magnetic metals (iron, cobalt, nickel) may bemagnetic, with low coercivity and high electrical resistance. The highresistance leads to low losses by eddy currents when subjected toalternating magnetic fields, a property useful, for example, astransformer magnetic cores.

Amorphous alloys may have a variety of potentially useful properties. Inparticular, they tend to be stronger than crystalline alloys of similarchemical composition, and they can sustain larger reversible (“elastic”)deformations than crystalline alloys. Amorphous metals derive theirstrength directly from their non-crystalline structure, which can havenone of the defects (such as dislocations) that limit the strength ofcrystalline alloys. For example, one amorphous metal, known asVITROLOY™, has a tensile strength that is almost twice that ofhigh-grade titanium. In some embodiments, metallic glasses at roomtemperature are not ductile and tend to fail suddenly when loaded intension, which limits the material applicability in reliability-criticalapplications, as the impending failure is not evident. Therefore, toovercome this challenge, metal matrix composite materials having ametallic glass matrix containing dendritic particles or fibers of aductile crystalline metal can be used. Alternatively, a BMG low inelement(s) that tend to cause embrittelment (e.g., Ni) can be used. Forexample, a Ni-free BMG can be used to improve the ductility of the BMG.

Another useful property of bulk amorphous alloys is that they can betrue glasses; in other words, they can soften and flow upon heating.This can allow for easy processing, such as by injection molding, inmuch the same way as polymers. As a result, amorphous alloys can be usedfor making sport equipment, medical devices, electronic components andequipment, and thin films. Thin films of amorphous metals can bedeposited as protective coatings via a high velocity oxygen fueltechnique.

A material can have an amorphous phase, a crystalline phase, or both.The amorphous and crystalline phases can have the same chemicalcomposition and differ only in the microstructure—i.e., one amorphousand the other crystalline. Microstructure in one embodiment refers tothe structure of a material as revealed by a microscope at 25×magnification or higher. Alternatively, the two phases can havedifferent chemical compositions and microstructures. For example, acomposition can be partially amorphous, substantially amorphous, orcompletely amorphous.

As described above, the degree of amorphicity (and conversely the degreeof crystallinity) can be measured by fraction of crystals present in thealloy. The degree can refer to volume fraction of weight fraction of thecrystalline phase present in the alloy. A partially amorphouscomposition can refer to a composition of at least about 5 vol % ofwhich is of an amorphous phase, such as at least about 10 vol %, such asat least about 20 vol %, such as at least about 40 vol %, such as atleast about 60 vol %, such as at least about 80 vol %, such as at leastabout 90 vol %. The terms “substantially” and “about” have been definedelsewhere in this application. Accordingly, a composition that is atleast substantially amorphous can refer to one of which at least about90 vol % is amorphous, such as at least about 95 vol %, such as at leastabout 98 vol %, such as at least about 99 vol %, such as at least about99.5 vol %, such as at least about 99.8 vol %, such as at least about99.9 vol %. In one embodiment, a substantially amorphous composition canhave some incidental, insignificant amount of crystalline phase presenttherein.

In one embodiment, an amorphous alloy composition can be homogeneouswith respect to the amorphous phase. A substance that is uniform incomposition is homogeneous. This is in contrast to a substance that isheterogeneous. The term “composition” refers to the chemical compositionand/or microstructure in the substance. A substance is homogeneous whena volume of the substance is divided in half and both halves havesubstantially the same composition. For example, a particulatesuspension is homogeneous when a volume of the particulate suspension isdivided in half and both halves have substantially the same volume ofparticles. However, it might be possible to see the individual particlesunder a microscope. Another example of a homogeneous substance is airwhere different ingredients therein are equally suspended, though theparticles, gases and liquids in air can be analyzed separately orseparated from air.

A composition that is homogeneous with respect to an amorphous alloy canrefer to one having an amorphous phase substantially uniformlydistributed throughout its microstructure. In other words, thecomposition macroscopically comprises a substantially uniformlydistributed amorphous alloy throughout the composition. In analternative embodiment, the composition can be of a composite, having anamorphous phase having therein a non-amorphous phase. The non-amorphousphase can be a crystal or a plurality of crystals. The crystals can bein the form of particulates of any shape, such as spherical, ellipsoid,wire-like, rod-like, sheet-like, flake-like, or an irregular shape. Inone embodiment, it can have a dendritic form. For example, an at leastpartially amorphous composite composition can have a crystalline phasein the shape of dendrites dispersed in an amorphous phase matrix; thedispersion can be uniform or non-uniform, and the amorphous phase andthe crystalline phase can have the same or a different chemicalcomposition. In one embodiment, they have substantially the samechemical composition. In another embodiment, the crystalline phase canbe more ductile than the BMG phase.

The methods described herein can be applicable to any type of amorphousalloy. Similarly, the amorphous alloy described herein as a constituentof a composition or article can be of any type. The amorphous alloy cancomprise the element Zr, Hf, Ti, Cu, Ni, Pt, Pd, Fe, Mg, Au, La, Ag, Al,Mo, Nb, Be, or combinations thereof. Namely, the alloy can include anycombination of these elements in its chemical formula or chemicalcomposition. The elements can be present at different weight or volumepercentages. For example, an iron “based” alloy can refer to an alloyhaving a non-insignificant weight percentage of iron present therein,the weight percent can be, for example, at least about 20 wt. %, such asat least about 40 wt. %, such as at least about 50 wt %, such as atleast about 60 wt. %, such as at least about 80 wt. %. Alternatively, inone embodiment, the above-described percentages can be volumepercentages, instead of weight percentages. Accordingly, an amorphousalloy can be zirconium-based, titanium-based, platinum-based,palladium-based, gold-based, silver-based, copper-based, iron-based,nickel-based, aluminum-based, molybdenum-based, and the like. The alloycan also be free of any of the aforementioned elements to suit aparticular purpose. For example, in some embodiments, the alloy, or thecomposition including the alloy, can be substantially free of nickel,aluminum, titanium, beryllium, or combinations thereof. In oneembodiment, the alloy or the composite is completely free of nickel,aluminum, titanium, beryllium, or combinations thereof.

For example, the amorphous alloy can have the formula (Zr, Ti)_(a)(Ni,Cu, Fe)_(b)(Be, Al, Si, B)_(c), wherein a, b, and c each represents aweight or atomic percentage. In one embodiment, a is in the range offrom 30 to 75, b is in the range of from 5 to 60, and c is in the rangeof from 0 to 50 in atomic percentages. Alternatively, the amorphousalloy can have the formula (Zr, Ti)_(a)(Ni, Cu)_(b)(Be)_(c), wherein a,b, and c each represents a weight or atomic percentage. In oneembodiment, a is in the range of from 40 to 75, b is in the range offrom 5 to 50, and c is in the range of from 5 to 50 in atomicpercentages. The alloy can also have the formula (Zr, Ti)_(a)(Ni,Cu)_(b)(Be)_(c), wherein a, b, and c each represents a weight or atomicpercentage. In one embodiment, a is in the range of from 45 to 65, b isin the range of from 7.5 to 35, and c is in the range of from 10 to 37.5in atomic percentages. Alternatively, the alloy can have the formula(Zr)_(a)(Nb, Ti)_(b)(Ni, Cu)_(c)(Al)_(d), wherein a, b, c, and d eachrepresents a weight or atomic percentage. In one embodiment, a is in therange of from 45 to 65, b is in the range of from 0 to 10, c is in therange of from 20 to 40 and d is in the range of from 7.5 to 15 in atomicpercentages. One embodiment of the described alloy system is aZr—Ti—Ni—Cu—Be based amorphous alloy under the trade name VITROLOY™,such as Vitreloy-1 and Vitreloy-101, as fabricated by LiquidmetalTechnologies, CA, USA. Some examples of amorphous alloys of thedifferent systems are provided in Table 1 and Table 2

TABLE 1 Amorphous Alloy Compositions  Alloy  At. % At. % At. % At. % At.% At. % At. % At. % 1 Fe Mo Ni Cr P C B 68.00%   5.00% 5.00% 2.00%12.50% 5.00% 2.50% 2 Fe Mo Ni Cr P C B Si 68.00%  5.00% 5.00% 2.00%11.00%  5.00%  2.50%  1.50%  3 Pd Cu Co P 44.48% 32.35%  4.05% 19.11%  4Pd Ag Si P 77.50%  6.00% 9.00%  7.50% 5 Pd Ag Si P Ge 79.00%  3.50%9.50%  6.00%  2.00% 5 Pt Cu Ag P B Si 74.70%  1.50% 0.30%  18.0%  4.00%1.50%

TABLE 2 Additional Amorphous Alloy Compositions Alloy Atm % Atm % Atm %Atm % Atm % Atm % 1 Zr Ti Cu Ni Be 41.20% 13.80% 12.50% 10.00% 22.50% 2Zr Ti Cu Ni Be 44.00% 11.00% 10.00% 10.00% 25.00% 3 Zr Ti Cu Ni Nb Be56.25% 11.25%  6.88%  5.63%  7.50% 12.50% 4 Zr Ti Cu Ni Al Be 64.75% 5.60% 14.90% 11.15%  2.60%  1.00% 5 Zr Ti Cu Ni Al 52.50%  5.00% 17.90%14.60% 10.00% 6 Zr Nb Cu Ni Al 57.00%  5.00% 15.40% 12.60% 10.00% 7 ZrCu Ni Al 50.75% 36.23%  4.03%  9.00% 8 Zr Ti Cu Ni Be 46.75%  8.25% 7.50% 10.00% 27.50% 9 Zr Ti Ni Be 21.67% 43.33%  7.50% 27.50% 10 Zr TiCu Be 35.00% 30.00%  7.50% 27.50% 11 Zr Ti Co Be 35.00% 30.00%  6.00%29.00% 12 Zr Ti Fe Be 35.00% 30.00%  2.00% 33.00% 13 Au Ag Pd Cu Si49.00%  5.50%  2.30% 26.90% 16.30% 14 Au Ag Pd Cu Si 50.90%  3.00% 2.30% 27.80% 16.00% 15 Pt Cu Ni P 57.50% 14.70%  5.30% 22.50% 16 Zr TiNb Cu Be 36.60% 31.40%  7.00%  5.90% 19.10% 17 Zr Ti Nb Cu Be 38.30%32.90%  7.30%  6.20% 15.30% 18 Zr Ti Nb Cu Be 39.60% 33.90%  7.60% 6.40% 12.50% 19 Cu Ti Zr Ni 47.00% 34.00% 11.00%  8.00% 20 Zr Co Al55.00% 25.00% 20.00%

Other ferrous metal-based alloys include compositions such as thosedisclosed in U.S. Patent Application Publication Nos. 2007/0079907 and2008/0118387. These compositions include the Fe(Mn, Co, Ni, Cu) (C, Si,B, P, Al) system, wherein the Fe content is from 60 to 75 atomicpercentage, the total of (Mn, Co, Ni, Cu) is in the range of from 5 to25 atomic percentage, and the total of (C, Si, B, P, Al) is in the rangeof from 8 to 20 atomic percentage, as well as the compositionFe₄₈Cr₁₅Mo₁₄Y₂C₁₅B₆. They also include the alloy systems described byFe—Cr—Mo—(Y, Ln)-C—B, Co—Cr—Mo-Ln-C—B, Fe—Mn—Cr—Mo—(Y, Ln)-C—B, (Fe, Cr,Co)—(Mo, Mn)—(C,B)—Y, Fe—(Co, Ni)—(Zr, Nb, Ta)—(Mo, W)—B, Fe—(Al,Ga)—(P, C, B, Si, Ge), Fe—(Co, Cr, Mo, Ga, Sb)—P—B—C, (Fe, Co)—B—Si—Nballoys, and Fe—(Cr—Mo)—(C,B)-Tm, where L_(n) denotes a lanthanideelement and T_(m) denotes a transition metal element. Furthermore, theamorphous alloy can also be one of the compositionsFe₈₀P_(12.5)C₅B_(2.5), Fe₈₀P₁₁C₅B_(2.5)Si_(1.5),Fe_(74.5)Mo_(5.5)P_(12.5)C₅B_(2.5), Fe_(74.5)Mo_(5.5)P₁₁C₅B_(2.5)Si_(1.5), Fe₇₀Mo₅Ni₅P_(12.5)C₅B_(2.5), Fe₇₀Mo₅Ni₅P₁₁C₅B_(2.5)Si_(1.5),Fe₆₈Mo₅Ni₅Cr₂P_(12.5)C₅B_(2.5), and Fe₆₈Mo₅Ni₅Cr₂P₁₁C₅B_(2.5)Si_(1.5),described in U.S. Patent Application Publication No. 2010/0300148.

The amorphous alloys can also be ferrous alloys, such as (Fe, Ni, Co)based alloys. Examples of such compositions are disclosed in U.S. Pat.Nos. 6,325,868; 5,288,344; 5,368,659; 5,618,359; and U.S. Pat. No.5,735,975, Inoue et al., Appl. Phys. Lett., Volume 71, p 464 (1997),Shen et al., Mater. Trans., JIM, Volume 42, p 2136 (2001), and JapanesePatent Application No. 200126277 (Pub. No. 2001303218 A). Onecomposition is Fe₇₂A₁₅Ga₂P₁₁C₆B₄. Another example isFe₇₂A₁₇Zr₁₀Mo₅W₂B₁₅. Another iron-based alloy system that can be used inthe coating herein is disclosed in U.S. Patent Application PublicationNo. 2010/0084052, wherein the amorphous metal contains, for example,manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon(0.3 to 3.1 atomic %) in the range of composition given in parentheses;and that contains the following elements in the specified range ofcomposition given in parentheses: chromium (15 to 20 atomic %),molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to16 atomic %), carbon (3 to 16 atomic %), and the balance iron.

The described amorphous alloy systems can further include additionalelements, such as additional transition metal elements, including Nb,Cr, V, and Co. The additional elements can be present at less than orequal to about 30 wt %, such as less than or equal to about 20 wt %,such as less than or equal to about 10 wt %, such as less than or equalto about 5 wt %. In one embodiment, the additional, optional element isat least one of cobalt, manganese, zirconium, tantalum, niobium,tungsten, yttrium, titanium, vanadium and hafnium to form carbides andfurther improve wear and corrosion resistance. Further optional elementsmay include phosphorous, germanium and arsenic, totaling up to about 2%,and preferably less than 1%, to reduce melting point. Otherwiseincidental impurities should be less than about 2% and preferably 0.5%.

Renewable Energy Resources

“The current energy supply depends mainly on fossil energy carriers . .. fossil fuels such as natural gas, petroleum, hard and brown coalneeded many thousands of years to form.” [Volker Quaschning.Understanding renewable energy systems, Copyright © Carl Hanser VerlagGmbH & Co KG, 2005, ISBN: 1-84407-128-6]. “However, due to theincreasing exploitation of the fossil reservoirs, future extraction willbe more and more difficult, technically challenging and risky andtherefore much more expensive than today. Deep-sea oil rigs are one stepin this development. If fossil fuel use continues unchecked, allavailable reserves of petroleum and natural gas will be exploited withinthe 21st century.” [Volker Quaschning. Understanding renewable energysystems, Copyright © Carl Hanser Verlag GmbH & Co KG, 2005, ISBN:1-84407-128-6]. “Thus, some decades from now, a few generations ofhumanity will have exploited the whole fossil energy reserves thatrequired millions of years to form.” [Volker Quaschning. Understandingrenewable energy systems, Copyright © Carl Hanser Verlag GmbH & Co KG,2005, ISBN: 1-84407-128-6] In addition to being a rapidly depletingresource, fossil fuels also have an adverse effect on the environment.If humanity does not “reduce anthropogenic greenhouse gas emissions, thecarbon dioxide concentration in the atmosphere will more than double bythe end of this century with respect to pre-industrial values. As aresult, the mean global temperature will rise more than 2° C.” [VolkerQuaschning. Understanding renewable energy systems, Copyright © CarlHanser Verlag GmbH & Co KG, 2005, ISBN: 1-84407-128-6] Therefore, thereis a pressing need for renewable energy resources. Renewable energyresources are “energy resources that are inexhaustible within the timehorizon of humanity. Renewable types of energy can be subdivided intothree areas: solar energy, planetary energy and geothermal energy.”[Volker Quaschning. Understanding renewable energy systems, Copyright ©Carl Hanser Verlag GmbH & Co KG, 2005, ISBN: 1-84407-128-6]

Solar Energy

Solar energy is a very potent renewable and sustainable energy resource.The energy of the sun striking the USA is about 2.8×10²³ Joules peryear, which is three thousand times for energy than the current USenergy consumption. Despite this vast surplus, only 10% of US annualenergy consumption. [“U.S. Energy InformationAdministration—EIA—Independent Statistics and Analysis.” How Much ofU.S. Energy Consumption and Electricity Generation Comes from RenewableEnergy Sources?—FAQ—U.S. Energy Information Administration (EIA), U.S.Energy Information Administration, 2018] There are two ways of producingelectricity using solar energy: Photovoltaic systems and ConcentratedSolar Power.

Photovoltaic Systems:

A photovoltaic system is composed of “one or more solar panels combinedwith an inverter and other electrical and mechanical hardware that useenergy from the Sun to generate electricity.” [J.M.K.C. Donev et al.(2018). Energy Education—Photovoltaic system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]] In this system, “the light from the Sun, made up ofpackets of energy called photons, falls onto a solar panel and createsan electric current. Each panel produces a relatively small amount ofenergy, but can be linked together with other panels to produce higheramounts of energy as a solar array.” [J.M.K.C. Donev et al. (2018).Energy Education—Photovoltaic system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]. However, “the electricity produced from a solar panel(or array) is in the form of direct current.” [J.M.K.C. Donev et al.(2018). Energy Education—Photovoltaic system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]].

Direct current is “an electric current that is uni-directional, so theflow of charge is always in the same direction.” [J.M.K.C. Donev et al.(2018). Energy Education—Alternating current [Online]. Available:https://energyeducation.ca/encyclopedia/Alternating_current. [Accessed:Aug. 11, 2019]]. However, the electrical utility grid which provides(and requires) alternating current (AC). Therefore, in order for thesolar electricity to be useful it must first be converted from DC to ACusing an inverter.” [J.M.K.C. Donev et al. (2018). EnergyEducation—Photovoltaic system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. An inverter is “an electrical device which acceptselectrical current in the form of direct current (DC) and converts it toalternating current (AC).” [J.M.K.C. Donev et al. (2018). EnergyEducation—Photovoltaic system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. Alternating current “[flips] the direction of chargeflow.” [J.M.K.C. Donev et al. (2018). Energy Education Alternatingcurrent [Online]. Available:https://energyeducation.ca/encyclopedia/Alternating_current. [Accessed:Aug. 11, 2019]]. The other components of a typical photovoltaic systeminclude “combiners, disconnects, breakers, meters and wiring.” [J.M.K.C.Donev et al. (2018). Energy Education—Photovoltaic_system [Online].Available: https://energyeducation.ca/encyclopedia/Photovoltaic_system.[Accessed: Aug. 11, 2019]]. A combiner in this case “combines two ormore electrical cables into one larger one.” [J.M.K.C. Donev et al.(2018). Energy Education—Photovoltaic_system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. Disconnects are “electrical gates or switches whichallow for manual disconnection of an electrical wire.” [J.M.K.C. Donevet al. (2018). Energy Education—Photovoltaic_system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. “The disconnects provide electrical isolation when aninverter needs to be installed or replaced.” [J.M.K.C. Donev et al.(2018). Energy Education—Photovoltaic_system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. Circuit breakers protect the circuits contained withinthe photovoltaic systems from damaging power surges. The electric meter“measures the amount of energy that passes through it and is commonlyused by electric utility companies to measure and charge customers.”[J.M.K.C. Donev et al. (2018). Energy Education—Photovoltaic_system[Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]]. The wiring is used to “transport the electrical energyfrom and between each component and must be properly sized to carry thecurrent.” [J.M.K.C. Donev et al. (2018). EnergyEducation—Photovoltaic_system [Online]. Available:https://energyeducation.ca/encyclopedia/Photovoltaic_system. [Accessed:Aug. 11, 2019]].

Concentrated Solar Power (CSP)

“Unlike solar (photovoltaic) cells, which use light to produceelectricity, concentrating solar power systems generate electricity withheat.” [Concentrating Solar Power: Energy From Mirrors,” U.S. Departmentof Energy, DOE/GO-102001-1147, March 2001.] Additionally, of all thetechnologies being developed for solar thermal power generation, centralreceiver systems (CRS) are able to work at the highest temperatures andto achieve higher efficiencies in electricity production” [IgnacioOrtega, J & Burgaleta, Juan & Tellez, Felix. (2008). Central ReceiverSystem Solar Power Plant Using Molten Salt as Heat Transfer Fluid.Journal of Solar Energy Engineering-Transactions of the ASME-J SOLENERGY ENG. 130. 10.1115/1.2807210.]. Concentrating solar collectors usemirrors and lenses to concentrate and focus sunlight onto a thermalreceiver. The receiver absorbs and converts sunlight into heat. The heatis then transported to a steam generator or engine where it is convertedinto electricity. There are three main types of CSP systems: parabolictroughs, dish/engine systems, and central receiver systems.

Trough systems use parabolic troughs lined with mirrors. These troughshave oil filled pipes running through the center. [“Concentrating SolarPower (CSP) Technologies.” Concentrating Solar Power (CSP) Technology,Solar Energy Development Programmatic EIS,solareis.anl.gov/guide/solar/csp/.]. The energy from the sun heats theoil which is flowing in the tubes, and the energy generated from theheat is used to create energy in a steam generator. [“ConcentratingSolar Power: Energy From Mirrors,” U.S. Department of Energy,DOE/GO-102001-1147, March 2001.]. Troughs are often placed in parallelrows, referred to as a collector field. The troughs are lined along anorth-south axis to ensure that the sun is always focusing on thereceiver as the day progresses.

Dish systems use “dish shaped parabolic mirrors as reflectors toconcentrate and focus the sun's rays onto a receiver, which is mountedabove the dish at the dish center.” [Concentrating Solar Power: EnergyFrom Mirrors,” U.S. Department of Energy, DOE/GO-102001-1147, March2001.]. The dish system is composed of a collector, receiver, andengine. The dish system operates by collecting and then concentratingthe sun's energy with the dish shaped surface “onto a receiver thatabsorbs the energy and transfers it to the engine. The engine thenconverts that energy to heat.” [Concentrating Solar Power: Energy FromMirrors,” U.S. Department of Energy, DOE/GO-102001-1147, March 2001.].

The heat is then converted into mechanical power. This occurs by thefollowing process: the working fluid is compressed when it is cold, thenthis compressed working fluid is heated. Then, it is expanded through aturbine or piston to generate mechanical power.

The third type of system, the central receiver system, has five maincomponents: heliostats, receiver, heat transport and exchange, thermalstorage, and controls. The central receiver system operates as follows:“thousands of individual sun-tracking mirrors called heliostats reflectsolar energy onto a receiver positioned on the top of a tall tower.Then, “the receiver collects the sun's heat in a heat-transfer fluid(molten salt) that flows through the receiver.” [Concentrating SolarPower: Energy From Mirrors,” U.S. Department of Energy,DOE/GO-102001-1147, March 2001.]. “The salt's heat energy is then usedto make steam to generate electricity in a conventional steamgenerator.” [Concentrating Solar Power: Energy From Mirrors,” U.S.Department of Energy, DOE/GO-102001-1147, March 2001.]. The molten saltstorage system retains heat in an efficient manner, so it can be storedup to days prior to being used to generate electricity.

Heat Transfer Fluids Used in CSP

In the CSP system, the heat transfer fluid is used in the receiver. Thereceiver “heats up due to the incoming solar radiation flux andtransmits heat to a heat transfer fluid. This fluid is usually water,air, or molten salt. The heat transfer fluid is then used, directly orindirectly, to run a turbine that produces electricity through agenerator.” [Murray, Daniel. (2012). Small-Scale Solar Central ReceiverSystem Design and Analysis.]. Substances considered to be goodcandidates for heat transfer fluids typically have “high thermalconductivities, such as liquid sodium, water/steam, or molten nitratesalt.” [Murray, Daniel. (2012). Small-Scale Solar Central ReceiverSystem Design and Analysis.].

Molten Salts

Molten salts present many advantages for use as the heat transfer fluidin the CSP system, including “a lower operating pressure and better heattransfer (and thus higher allowable incident flux) than a water/steamreceiver. This translates into a smaller, more efficient, and lower costreceiver and support tower. In addition, the relatively inexpensive saltcan be stored in large tanks at atmospheric pressure, allowing 1)economic and efficient storage of thermal power collected early in theday for use during peak demand periods; 2) increased plant capacityfactor by oversizing of the collector and receiver systems with storageof the excess thermal energy for electricity generation in the evening;3) isolation of the turbine-generator from solar energy transients; and4) operation of the turbine at maximum efficiency.” [Tyner, C. E.,Sutherland, J. P., and Gould, W. R. Jr. Solar two: A molten salt powertower demonstration. United States: N. p., 1995. Web.]. “To date, SolarEnergy Technologies Office (SETO) has identified molten chloride salts(for example, a eutectic mixture of KCl—MgCl₂, among other possiblecompositions) as a highly promising heat transfer fluid (HTF) andthermal energy storage (TES) media capable of operating between 550° C.and 750° C.” [FY2017 Phase I Release II Solicitation].

TABLE 3 Cooling Materials Properties Estimated Heat Transfer EutecticBoiling Heat Raw Materials Ranking at 700° C. [° C.] [° C.] CapacityCosts $/L at Laminar Turbulent Temperature Temperature [cal/g-° C.] 700C. Water 0.63 4.84 — 100 1 — (calcs done at 300° C.) Pb 5.36 28.53 —1749 0.031 4.1 KCl—MgCl₂ 7.74 21.08 426 >1418 0.229 0.35 NaCl—MgCl₂ 7.8121.7 475 >1465 0.262 0.42 LiF—NaF—KF 6.61 13.3 454 1570 0.387 15.79

Theory of Corrosion of Metals:

Corrosion is defined as “destructive and unintentional degradation of amaterial caused by its environment.” [School of Materials Science andEngineering.” 1: What Is Corrosion?|School of Materials Science andEngineering, UNSW Sydney, 12 Dec. 2013.]. Metals are particularlysusceptible to corrosion, and nearly all “environments can causecorrosion to some degree, since the corroded state is the more stablestate.” [School of Materials Science and Engineering.” 1: What IsCorrosion?|School of Materials Science and Engineering, UNSW Sydney, 12Dec. 2013]. Corrosion can be classified in different ways, such as:“chemical and electrochemical, high temperature and low temperature, andwet corrosion and dry corrosion.” [Corrosion: Introduction —Definitionsand Types.” NP TEL Web Course, National Programme on Technology EnhancedLearning, nptel.ac.in/courses/113108051/module1/lecture1.pdf]

Dry corrosion occurs in the absence of aqueous “environment[s], usuallyin the presence of gases and vapors, mainly at high temperatures.”[Corrosion: Introduction—Definitions and Types.” NPTEL Web Course,National Programme on Technology Enhanced Learning,nptel.ac.in/courses/113108051/module1/lecture1.pdf]. Steel, a metalcommonly used in piping and various other applications, is verysusceptible to corrosion. The corrosion of steel is an electrochemicalreaction. It involves the ionization of “metal atoms and the loss ofthese ions into solution or into a corrosion product. Since theionization reaction means giving up electrons, a flow of electrons awayfrom the site of this reaction must occur to avoid a build-up ofnegative charge.” [Sniderman, Debbie. “Salt Heat Transfer Fluids inCSP.” ASME, The American Society of Mechanical Engineers, 1 Feb. 2012].Another type of corrosion is pitting type corrosion. “Pitting corrosionis localized accelerated dissolution of metal that occurs as a result ofa breakdown of the otherwise protective passive film on the metalsurface.” [Frankel, G. S. “Pitting Corrosion of Metals.” Journal of TheElectrochemical Society, vol. 145, no. 6, 1998, pp. 2186-2198,doi:10.1149/1.1838615.].

Passivity is a “loss of electrochemical reactivity (drastic decrease incorrosion rate) that many engineering alloys (e.g. stainless steel,Ni-based alloys, Al alloys) exhibit under certain environmentalconditions.” [“Passivity.” Electroanalytical Chemistry, Michigan StateUniversity, 2016]. Passivation “is the result of the presence of a thinprotective oxide or oxyhydroxide passive film on the metal surface.”[“Passivity.” Electroanalytical Chemistry, Michigan State University,2016]. There is a thin shell of protection against corrosion. However,this passive film or passivation layer is “susceptible to localizedbreakdown resulting in accelerated dissolution of the underlying metal.[“Frankel, G. S. “Pitting Corrosion of Metals.” Journal of TheElectrochemical Society, vol. 145, no. 6, 1998, pp. 2186-2198,doi:10.1149/1.1838615.].

“Pitting corrosion will only occur in the presence of aggressive anionicspecies, and chloride ions are usually, although not always, the cause”[Frankel, G. S. “Pitting Corrosion of Metals.” Journal of TheElectrochemical Society, vol. 145, no. 6, 1998, pp. 2186-2198,doi:10.1149/1.1838615.]. “Pitting is considered to be autocatalytic innature; once a pit starts to grow, the conditions developed are suchthat further pit growth is promoted.” [Frankel, G. S. “Pitting Corrosionof Metals.” Journal of The Electrochemical Society, vol. 145, no. 6,1998, pp. 2186-2198, doi:10.1149/1.1838615.]. Amorphous metals are morecorrosion resistant compared to conventional metals due to the lack oflong-range periodicity, related grain boundaries and crystal defectssuch as dislocations. In addition, they are stronger than crystallinemetals and they can sustain larger reversible deformations thancrystalline alloys (FIG. 2 ). Due to their unique microstructure,amorphous metals combine ultrahigh strength, high hardness and ductilityin one single material.

Molten Salt Corrosion:

Molten salts are candidates “for CSP applications because of their highdecomposition temperatures and good thermal properties; but they can becorrosive to common alloys used in vessels, heat exchangers, and pipingat these elevated temperatures” [Ho, Clifford K. Advances in centralreceivers for concentrating solar applications. United States: N. p.,2017. Web. doi:10.1016/j.solener.2017.03.048.]. For example, in a testconducted involving molten chloride salt, “bare stainless steel alloystested in a molten chloride corroded as fast as 4,500 micrometers peryear” [News Release: NREL Investigates Coatings Needed for ConcentratingSolar Power.” NREL.gov, National Renewable Energy Laboratory, 18 Sept.2018].

In addition, 316L stainless steel, which is commonly used in CSPapplications, corrodes under molten salt environments. “Containmentmaterial degradation is a major concern to meet commercial viability ofnext generation CSP plants” [Gomez-Vidal, Judith C., and Tirawat,Robert. Corrosion of alloys in a chloride molten salt (NaCl-LiCl) forsolar thermal technologies. United States: N. p., 2016. Web.doi:10.1016/j.solmat.2016.05.052.] 316L stainless steel (SS) is commonlyas piping used due to its mechanical durability, resistance againstcorrosion under severe environment and cost of material. However, 316LSS corrodes under molten salt environment since the chromium oxideprotection layer gets destroyed and pitting type corrosion occurs.

Materials Demonstrating Essential Properties:

Materials used under molten salt environments at high temperaturesshould have the following properties: Strength over time, long-termcreep, and corrosion resistance to molten salts. [C.W. Forsberg: TheAdvanced High-Temperature Reactor: High Temperature Fuel, Liquid SaltCoolant, Liquid-Metal-Reactor Plant,” Prog. Nucl. Energy, (2005) 4732-43]. In a recent research work done from Savannah River NationalLaboratory, University of South Carolina and University of Alabama,different kinds of Ni-based alloys have been tested under moltenchloride salt environment. The research showed that Incoloy 800H has thehighest general corrosion rate but does not show any localizedcorrosion. Haynes NS163 shows second highest general corrosion despitebeing a Co based alloy and localized corrosion, while Haynes 230 showslowest corrosion with passivation until Ni oxidized (passive layerbreaks down). The research summarized that all Ni-based alloys testedhave corrosion potentials between 2.26 and 2.31V and explained thatcorrosion occurs along boundaries in alloys. Researcher at Oak RidgeNational Laboratory (ORNL) and Idaho National Laboratory testedcorrosion resistance of various alloys under KCl-MgCl₂ molten saltenvironment. They showed that Haynes 230 exhibited the least mass lossfrom the exposure to molten KCl—MgCl₂, while Hastelloy N exhibited theleast grain boundary attack and chromium dissolution. Despite moderatemass loss, 316 stainless steel (SS) exhibited the worst grain boundaryattack with chromium depletion to 300 micrometers depth during the 100hours exposure. Luke Olson and Sridharan, et al also measured corrosionrates of different alloys in KCl—MgCl₂ molten environment (Table 2).

TABLE 4 Comparison of corrosion rates of various alloys at 850° C. byusing quartz crucible Alloy Corrosion rate [mm/y] Hastelloy N 1.1Hastelloy X 1.1 Inconel 617 1.3 Haynes 230  0.67 Incoloy 800H 1.4

However, the ultimate tensile strength of all Ni-based alloys reducesrapidly after 600° C. Cho et al. studied and modelled the corrosionresistance of Fe—Ni—Cr alloy under KCl—MgCl₂ at a temperature range of700° C. to 1,000° C. The experiment results and the model predictionsshowed that the selective Cr corrosion is mass transfer driven and thedepletion could be further increased in CSP systems with forcedconvection. Several coatings including iron- and nickel-based alloys,nickel electroplating, molybdenum thermal spray, and diamond likecoatings and post-processing techniques were investigated at Universityof Wisconsin-Madison. They showed that Ni-electroplated coatings werethe most promising, while Mo thermal spray and diamond like carboncoatings had spalling issues. The Ni-plating was shown to greatly reducethe rate of corrosion due to chromium dealloying from the base alloy.

The materials that are most promising with regards to fulfilling thethree criteria mentioned previously in this section are amorphous alloyscontaining metals such as Fe, Cr, Cu, Ni, Co, Al, Mo, Ti, Si, as well asnonmetals such as C, B, and others.

Spraying Process which Ensures Amorphous Structure is Retained

The amorphous coating can be in powder or wire form and sprayed usingconventional thermal spraying techniques. The thermal spraying techniquecould be used to apply the material onto the substrate. The mainadvantages of using the thermal spraying technique include the fact thata wide range of materials (polymers, metals, metallic alloys, ceramicsand composites) can be used as the feedstock, almost all substrates canbe coated. Additionally, there is low thermal stress on the substrateparts (meaning that the substrate will not melt), high deposition rates.The thermal spraying process is available as a field service, meaningthe process can occur on the client's property. Lastly, thermal sprayingis suitable for large scale components coating, and coating of complexgeometries. The thermal spraying process, combined with the structure ofthe invention, ensures that the amorphous structure of the sprayedamorphous material is retained, since the cooling rate during thisprocess is in the range of 1×10⁸ K/s. This rate is sufficiently high toensure that crystallization will not occur, since “The minimum coolingrates for glass formation has been reported to be above 10-10⁴ K/s forFe-, Co- and Ni-based amorphous alloys.” [010-005]. The connectionbetween the amorphous state and the glass state is that “amorphousmetals have a . . . glassy structure” [from their paper]. The amorphouscoatings have high wear resistance, low coefficient of friction, highcorrosion resistance, and adjusted thermal expansion coefficient.

Advantages

Advantages of the disclosed embodiments include providing an amorphousbased alloy which provides full corrosion resistance against moltensalts, including at high temperatures. The amorphous based metalcoatings offer novel performance and cost breakthroughs. The amorphousalloys offer: corrosion protection against severe corrosion, corrosionprotection at high temperatures, corrosion protection against moltenchloride salt, corrosion protection against molten fluoride salt,corrosion protection against molten sulphate salt, erosion/corrosionprotection, and the fact that material could be in powder or wire formand sprayed using conventional thermal sprayed techniques including,HVOF, cold spraying, twin arc and plasma Spraying.

The advantages are: unique structure with a controlled chemicalcomposition, high corrosion resistance (no corrosion signs after 300hours testing at 750° C.), wear characteristics better than Ni-basedalloys, dense coatings without cracks, corrosion resistant chemistry andbetter than current WC-based coatings. Additional advantages are highstrength-to-weight ratio (for example amorphous alloys have astrength-to-weight ratio 1.9×higher than titanium:amorphous alloys witha strength 2,000-3,500 MPa and density 5-7 g/cm³ have astrength-to-weight ratio of 400-500, while titanium alloys have astrength-to-weight ratio is 260 with a strength of 1,250 MPa anddensity; a strength-to-weight ratio of 3.3×higher than Inconel:Inconelstrength 1,250 MPa and density 8.28 g/cm³), Adjustable thermal expansioncoefficient according to the base materials (usually steel or Ni-basedalloy), Superior spallation resistance for highly stressed parts due tothe amorphous structure, lo limitation on parts geometry and dimensions.and significantly lower cost.

EMBODIMENTS

An embodiment relates to material comprising an amorphous metal ceramiccomposite, wherein the material exhibits corrosion resistance to amolten potassium chloride salt or a molten magnesium chloride salt at atemperature up to 800° C.

In an embodiment, the material is configured to be a component of asolar concentrator and the material in the component has an ability towithstand temperatures up to 800° C. without corrosion in the presenceof molten chloride salt such as potassium magnesium chloride salt orcarnalite salt.

In an embodiment, the material is configured to be a coating and thematerial in the coating has an ability to withstand temperatures up to800° C. without corrosion in the presence of molten chloride salt suchas potassium magnesium chloride salt or carnallite salt.

An embodiment relates to material comprising an amorphous metal ceramiccomposite, wherein the material exhibits corrosion resistance for atleast 30 years to a molten chloride salt such as potassium magnesiumchloride salt or carnallite salt at temperatures up to 800° C.

An embodiment relates to material comprising an amorphous metal ceramiccomposite, wherein the material exhibits a higher corrosion resistancethan that of Haynes 230 to a chloride salt such as potassium magnesiumchloride salt or carnallite salt at temperatures up to 800° C.

An embodiment relates to material that is formed from an amorphousmaterial that is partially or fully amorphous comprising of an alloy,wherein the amorphous material is either thermally and/or non-thermallysprayed as a coating and heated to a temperature above 600° C. Thecoating remains unchanged up to 600° C. In an embodiment, above 600° C.,the amorphous material in the coating converts to a partially or fullycrystalline material. In an embodiment, above 600° C., the amorphousmaterial in the coating converts to an amorphous metal ceramiccomposite.

An embodiment relates to material that is formed from an amorphousmaterial that is partially or fully amorphous comprising a nickel-basedalloy and/or an iron-based alloy, wherein the amorphous material isthermally sprayed as a coating and heated to a temperature above 600° C.The coating remains unchanged up to 600° C. In an embodiment, above 600°C., the amorphous material in the coating converts to a partially orfully crystalline material. In an embodiment, above 600° C., theamorphous material in the coating converts to an amorphous metal ceramiccomposite.

An embodiment relates to material that is formed from an amorphousmaterial that is partially or fully amorphous comprising other than anickel-based alloy and/or an iron-based alloy, wherein the amorphousmaterial is thermally sprayed as a coating and heated to a temperatureabove 600° C. The coating remains unchanged up to 600° C. In anembodiment, above 600° C., the amorphous material in the coatingconverts to a partially or fully crystalline material. In an embodiment,above 600° C., the amorphous material in the coating converts to anamorphous metal ceramic composite.

In an embodiment, the amorphous metal ceramic composite comprises athermal ceramic containing a combination of borides and carbides. Theamorphous metal ceramic composite is not fully amorphous above 600° C.,but still exhibits corrosion resistance to a molten potassium chloridesalt or a molten magnesium chloride salt at temperatures up to 800° C.

In an embodiment the material comprising an amorphous metal ceramiccomposite is not corroded for 300 hours, at 750° C. whereas Haynes 230corrodes within 300 hours at 750° C.

In an embodiment the material comprising an amorphous metal ceramiccomposite are corrosion resistant at temperature about 400° C. to 500°C.

In an embodiment the material comprising an amorphous metal ceramiccomposite are component of a system such as a pump or a tank or a pipe,wherein the system stores chlorides/salts and/or pump chlorides/saltsfrom one place to another. In an embodiment the material comprising anamorphous metal ceramic composite are component of a nuclear facilityand/or a nuclear reactor employing chlorides for a better efficiency ofthe energy.

In an embodiment the material comprising an amorphous metal ceramiccomposite is component of a power supply such as a battery.

An embodiment relates to renewable energy resources and the need forcorrosion resistance to molten salts. The most generic form of thispatent is a material coating used to cover pipes used in the renewableenergy sector. This material presented in this patent is an amorphousmetal-based coating that transforms to a ceramic at temperatures above600° C. There are many attractive properties resulting from thistransformation. Aside from maintaining the corrosion resistance, theproperties the ceramic has are: unique structure with a controlledchemical composition, high corrosion resistance (no corrosion signsafter 300 hours testing at 750° C.), wear characteristics better thanNi-based alloys and better than current WC-based coatings.

In an embodiment the material comprising an amorphous metal ceramiccomposite has high strength-to-weight ratio (for example amorphousalloys have a strength-to-weight ratio 1.9× higher thantitanium:amorphous alloys with a strength 2,000-3,500 MPa and density5-7 g/cm³ have a strength-to-weight ratio of 400-500, while titaniumalloys have a strength-to-weight ratio is 260 with a strength of 1,250MPa and density; a strength-to-weight ratio of 3.3×higher thanInconel:Inconel strength 1,250 MPa and density 8.28 g/cm³), adjustablethermal expansion coefficient according to the base materials (usuallysteel or Ni-based alloy), superior spallation resistance for highlystressed parts due to the amorphous structure, no limitation on partsgeometry and dimensions, and a significantly lower cost.

In an embodiment the material comprising an amorphous metal ceramiccomposite has strength over time, long-term creep, and corrosionresistance to molten salts. If the materials to which this coating wereto be applied to did not have the coating on it, it would experiencepitting type corrosion, which is localized breakdown and dissolution ofthe metal.

An embodiment relates to concentrated solar power systems, or CSP, andthe need for corrosion resistance to molten salts.

An embodiment relates to concentrating solar collectors that use mirrorsand lenses to concentrate and focus sunlight onto a thermal receiver.The receiver absorbs and converts sunlight into heat.

In an embodiment the material is an amorphous metal-based coating thattransforms to a ceramic at temperatures such as 500° C., or such as 600°C., or such as 650° C. or such as 700° C. The amorphous metal ceramiccomposite has controlled chemical composition, high corrosion resistance(no corrosion signs after 300 hours testing at 750° C.), wearcharacteristics better than Ni-based alloys and better than currentWC-based coatings. In addition, the amorphous metal ceramic compositehas high strength-to-weight ratio (for example amorphous alloys have astrength-to-weight ratio 1.9×higher than titanium:amorphous alloys witha strength 2,000-3,500 MPa and density 5-7 g/cm³ have astrength-to-weight ratio of 400-500, while titanium alloys have astrength-to-weight ratio is 260 with a strength of 1,250 MPa anddensity; a strength-to-weight ratio of 3.3×higher than Inconel:Inconelstrength 1,250 MPa and density 8.28 g/cm³), adjustable thermal expansioncoefficient according to the base materials (usually steel or Ni-basedalloy), superior spallation resistance for highly stressed parts due tothe amorphous structure, no limitation on parts geometry and dimensions,and a significantly lower cost.

In an embodiment the material comprising an amorphous metal ceramiccomposite has strength over time, long-term creep, and corrosionresistance to molten salts

An embodiment relates to heat transfer fluids used in CSP systems, andthe need for corrosion resistance to molten salts. In the CSP system,the heat transfer fluid is used in the receiver. The receiver heats tothe incoming solar radiation flux and transmits heat to a heat transferfluid. This fluid is usually water, air, or molten salt. The heattransfer fluid is used, directly or indirectly, to run a turbine toproduce electricity through a generator.

In an embodiment the material comprising an amorphous metal ceramiccomposite has: strength over time, long term creep, and corrosionresistance to molten salts.

In an embodiment the material is formed from an amorphous materialcomprising an alloy containing metals such as Fe, Cr, Cu, Ni, Co, Al,Mo, Ti, metalloid such as Si as well as nonmetals such as C, B, etc.

An embodiment relates to a process of forming the material from anamorphous material that is partially or fully amorphous material. The isformed from an amorphous material, when combined with the uniquestructure of the inventive materials, ensure that the amorphousstructure of sprayed amorphous materials is retained since the coolingrate during thermal spraying process is in the range of 1×10⁸K/s[Systems and methods for fabricating objects including amorphous metalusing techniques akin to additive manufacturing, US 20140202595 A1].This spraying process is called thermal spraying, and it can be used toapply the material in powder or wire form. The thermal sprayingtechnique could be used to apply the material onto the substrate. Themain advantages of using the thermal spraying technique include the factthat a wide range of materials (polymers, metals, metallic alloys,ceramics and composites) can be used as the feedstock, almost allsubstrates can be coated. Additionally, there is low thermal stress onthe substrate parts (meaning that the substrate will not melt), highdeposition rates. The thermal spraying process is available as a fieldservice, meaning the process can occur on the client's property. Lastly,thermal spraying is suitable for large scale components coating, andcoating of complex geometries. The thermal spraying process, combinedwith the structure of the invention, ensures that the amorphousstructure of the sprayed amorphous material is retained, since thecooling rate during this process is in the range of 1×10⁸ K/s. This rateis sufficiently high to ensure that crystallization will not occur,since “The minimum cooling rates for glass formation has been reportedto be in the range of 10-10⁴ K/s for Fe-, Co- and Ni-based amorphousalloys.” [010-005]. The connection between the amorphous state and theglass state is that amorphous metals have a glassy structure.

Coatings feature high ductility, high hardness, superior spallationresistance for highly stressed parts, high wear resistance and lowfriction through the appropriate structure and composition. Thesecoatings can be catered to a variety of applications to meet evolvingtechnology requirements, with the following material properties ofinterest for engine/driveline systems materials: high wear resistance;low coefficient of friction; high corrosion resistance; and adjustedthermal expansion coefficient.

This material presented in this patent is an amorphous metal-basedcoating that transforms to a ceramic at temperatures such as above 600°C., such as 600° C., such as 650° C. or such as 700° C. There are manyattractive properties resulting from this transformation. Aside frommaintaining the corrosion resistance, the properties the ceramic hasare: unique structure with a controlled chemical composition, highcorrosion resistance, wear characteristics better than Ni-based alloysand better than current WC-based coatings. In addition, the ceramicmaterial has high strength-to-weight ratio (for example amorphous alloyshave a strength-to-weight ratio 1.9× higher than titanium:amorphousalloys with a strength 2,000-3,500 MPa and density 5-7 g/cm³ have astrength-to-weight ratio of 400-500, while titanium alloys have astrength-to-weight ratio is 260 with a strength of 1,250 MPa anddensity; a strength-to-weight ratio of 3.3× higher than Inconel:Inconelstrength 1,250 MPa and density 8.28 g/cm³), adjustable thermal expansioncoefficient according to the base materials (usually steel or Ni-basedalloy), superior spallation resistance for highly stressed parts due tothe amorphous structure, no limitation on parts geometry and dimensions,and a significantly lower cost. In order for a material to be effectiveat resisting corrosion under molten salt environments, it must have thefollowing properties: corrosion resistance to molten salts, strengthover time and long-term creep, and. If the materials to which thiscoating were to be applied to did not have the coating on it, it wouldexperience intergranular type corrosion, which is localized breakdownand dissolution of the metal. Current products available on the marketoffer only lackluster performance.

EXAMPLES Example 1

An embodiment relates to an Ni based amorphous alloy which providescorrosion resistance against molten salts. The amorphous metal Ni basedalloy 1 is prepared from the proper elements in powdered form. Thepowder comprising the Ni based amorphous alloy 1 (marked Ni-4) isapplied to a substrate by a High Velocity Oxy-Fuel (HVOF) thermalspraying process. Preferably the said powder has a particle size from 10micrometers to 60 micrometers. The thermal spraying melts the particles,then atomizes them and sprays them onto the substrate at highvelocities, quenching on the substrate and providing an amorphouscoating. Another layer was applied, using the same process, and bondedwith the previous layer. To test the efficacy of the coating incorrosion resistance, samples with dimensions 20×10×2 mm and from Haynes230 (Alloy 230) were prepared. Three samples each of coated sample wereexposed, along with samples of uncoated Haynes 230. Samples were exposedto molten KCl—MgCl₂ in a 68/32 ratio for 300 hours at 750° C. Opticalmicrographs of representative samples before and after exposure areshown in FIG. 3 . After the exposure time is finished, the capsules wereflipped vertically to allow the salt mixture to drain from the samplesurface, and the capsules were cooled in room temperature. The sampleswere metallographically mounted and polished to examine the crosssections. As expected, the uncoated alloy Haynes 230 specimens exhibitedsignificant intergranular attack. The coated specimens showed no attackon the base alloy Haynes 230 at all. As expected, the uncoated Alloy 230samples had significant Cr depletion along grain boundaries near thesurfaces. The coated samples not only showed no Cr depletion in the basemetal but exhibited no Cr depletion in the coatings either. The depth ofattack was measured on uncoated samples (40 measurements per sample)based on the SEM-EDS analysis. The median depth of attack is 33 μm for300 hours. This material presented in this patent is an amorphousmetal-based coating that transforms to a ceramic at temperatures above600° C. There are many attractive properties resulting from thistransformation. Aside from maintaining the corrosion resistance, theproperties the ceramic has are: unique structure with a controlledchemical composition, high corrosion resistance (no corrosion signsafter 300 hours testing at 750° C.) and wear characteristics better thanNi-based alloys, dense coatings without cracks and corrosion resistantchemistry. In addition, the ceramic material has high strength-to-weightratio (for example amorphous alloys have a strength-to-weight ratio 1.9×higher than titanium:amorphous alloys with a strength 2,000-3,500 MPaand density 5-7 g/cm³ have a strength-to-weight ratio of 400-500, whiletitanium alloys have a strength-to-weight ratio is 260 with a strengthof 1,250 MPa and density; a strength-to-weight ratio of 3.3× higher thanInconel:Inconel strength 1,250 MPa and density 8.28 g/cm³), adjustablethermal expansion coefficient according to the base materials (usuallysteel or Ni-based alloy), superior spallation resistance for highlystressed parts due to the amorphous structure, no limitation on partsgeometry and dimensions, and a significantly lower cost. In order for amaterial to be effective at resisting corrosion under molten saltenvironments, it must have the following properties: Strength over time,long-term creep, and corrosion resistance to molten salts. If thematerials to which this coating were to be applied to did not have thecoating on it, it would experience intergranular type corrosion, whichis localized breakdown and dissolution of the metal. Current productsavailable on the market offer only lackluster performance.

Example 2

The powder comprising the Ni based amorphous alloy 2 (marked Ni-3) isapplied to a substrate by a High Velocity Oxy-Fuel (HVOF) thermalspraying process. Preferably the said powder has a particle size from 10micrometers to 60 micrometers. The thermal spraying melts the particles,then atomizes them and sprays them onto the substrate at highvelocities, quenching on the substrate and providing an amorphouscoating. Another layer was applied, using the same process, and bondedwith the previous layer. To test the efficacy of the coating incorrosion resistance, samples with dimensions 20×10×2 mm and from Haynes230 (Alloy 230) were prepared. Three samples each of coated sample wereexposed, along with samples of uncoated Haynes 230. Samples were exposedto molten KCl—MgCl₂ in a 68/32 ratio for 300 hours at 750° C. Opticalmicrographs of representative samples before and after exposure areshown in FIG. 3 . After the exposure time is finished, the capsules wereflipped vertically to allow the salt mixture to drain from the samplesurface, and the capsules were cooled in room temperature. The sampleswere metallographically mounted and polished to examine the crosssections. As expected, the uncoated alloy Haynes 230 specimens exhibitedsignificant intergranular attack. The coated specimens showed no attackon the base alloy Haynes 230 at all. FIG. 4 shows a close-up of theintergranular attack on an uncoated Alloy 230 samples. The crosssections were also examined with SEM and SEM-EDS and the results areshown in FIG. 5 -FIG. 6 . As expected, the uncoated Alloy 230 sampleshad significant Cr depletion along grain boundaries near the surfaces.The coated samples not only showed no Cr depletion in the base metal butexhibited no Cr depletion in the coatings either. The depth of attackwas measured on all uncoated samples (40 measurements per sample) basedon the SEM-EDS analysis and is shown in FIG. 7 . The median depth ofattack is 33 μm for 300 hours. This material presented in this patent isan amorphous metal-based coating that transforms to a ceramic attemperatures above 600° C. There are many attractive propertiesresulting from this transformation. Aside from maintaining the corrosionresistance, the properties the ceramic has are: Unique structure with acontrolled chemical composition, high corrosion resistance (no corrosionsigns after 300 hours testing at 750° C.) and wear characteristicsbetter than Ni-based alloys. In addition, the ceramic material has highstrength-to-weight ratio (for example amorphous alloys have astrength-to-weight ratio 1.9× higher than titanium:amorphous alloys witha strength 2,000-3,500 MPa and density 5-7 g/cm³ have astrength-to-weight ratio of 400-500, while titanium alloys have astrength-to-weight ratio is 260 with a strength of 1,250 MPa anddensity; a strength-to-weight ratio of 3.3× higher than Inconel:Inconelstrength 1,250 MPa and density 8.28 g/cm³), adjustable thermal expansioncoefficient according to the base materials (usually steel or Ni-basedalloy), superior spallation resistance for highly stressed parts due tothe amorphous structure, no limitation on parts geometry and dimensions,and a significantly lower cost. In order for a material to be effectiveat resisting corrosion under molten salt environments, it must have thefollowing properties: strength over time, long-term creep, and corrosionresistance to molten salts. If the materials to which this coating wereto be applied to did not have the coating on it, it would experienceintergranular type corrosion, which is localized breakdown anddissolution of the metal. Current products available on the market offeronly lackluster performance.

Example 3

The powder comprising the Fe based amorphous alloy is applied to asubstrate by a High Velocity Oxy-Fuel (HVOF) thermal spraying process.Preferably the said powder has a particle size from 10 micrometers to 60micrometers. The thermal spraying melts the particles, then atomizesthem and sprays them onto the substrate at high velocities, quenching onthe substrate and providing an amorphous coating. Another layer wasapplied, using the same process, and bonded with the previous layer. TheFe-based coatings are fully amorphous up to 650° C. and start tocrystallize after it. At 750° C., 87% of the coating was crystallized.The coating still provides the full corrosion resistance that it didwhen it was amorphous. The crystallinity was estimated by the area ratioof the major peaks of the heat-treated samples to that of the coating inas-sprayed conditions. The cooling rate was too slow to know exactly ifthe crystallization was a result of the cooling process or if thecrystallization started at the peak temperature (750° C. in this case).The samples after corrosion testing were tested by using XRD. The X-raypattern of the samples after molten salt testing are consistent with theX-ray diffraction results of heat-treated samples in inert atmosphere.However, the peaks intensity on the samples that was immersed in moltensalt are different compared to the heat-treated sample under the sametemperature. That could be explained either through different coolingrates of the samples or through the different holding time. However, inboth cases hard phases of chromium boride, chromium carbide, molybdenumboride and ternary carbide of ferro-molybdenum were identified in a highconcentrated chromium phase (Cr0.7Fe0.3) matrix. Same observations weredone for the Ni-based coatings. Both of them are also crystallized aftermolten corrosion testing. This material presented in this patent is anamorphous metal-based coating that transforms to a ceramic attemperatures above 600° C. There are many attractive propertiesresulting from this transformation. Aside from maintaining the corrosionresistance, the properties the ceramic has are: unique structure with acontrolled chemical composition, high corrosion resistance (no corrosionsigns after 300 hours testing at 750° C.) and wear characteristicsbetter than Ni-based alloys, (dense coatings without cracks andcorrosion resistant chemistry). In addition, the ceramic material hashigh strength-to-weight ratio (for example amorphous alloys have astrength-to-weight ratio 1.9× higher than titanium:amorphous alloys witha strength 2,000-3,500 MPa and density 5-7 g/cm³ have astrength-to-weight ratio of 400-500, while titanium alloys have astrength-to-weight ratio is 260 with a strength of 1,250 MPa anddensity; a strength-to-weight ratio of 3.3× higher than Inconel:Inconelstrength 1,250 MPa and density 8.28 g/cm³), adjustable thermal expansioncoefficient according to the base materials (usually steel or Ni-basedalloy), superior spallation resistance for highly stressed parts due tothe amorphous structure, no limitation on parts geometry and dimensions,and a significantly lower cost. In order for a material to be effectiveat resisting corrosion under molten salt environments, it must have thefollowing properties: strength over time, long-term creep, and corrosionresistance to molten salts. If the materials to which this coating wereto be applied to did not have the coating on it, it would experienceintergranular type corrosion, which is localized breakdown anddissolution of the metal. Current products available on the market offeronly lackluster performance.

Example 4

The amorphous metal Ni based alloy 1 is prepared from Cr, Ni, Fe Si, B,and C in powdered form. The amorphous alloy is substantially free of Moand C where there is less than 5 wt. % of Mo or C.

Example 5

The amorphous Ni based alloy 2 is prepared from the Cr, Ni, Mo, Cu, Co,Fe, B, Si, and C in powdered form. The amorphous alloy is generally freeof B, C, and Si, where there is between 0 to 30 wt. % B, C, and Si.

Example 6

The amorphous metal Fe based alloy is prepared from the Fe, Cr, Mo, B,Si and C in powdered form. The amorphous alloy is generally free of B,C, Si, where there is between 0 to 10 wt. % of these elements.

Example 7

The powder comprising the Ni based amorphous alloy 1 is applied to asubstrate by a High Velocity Oxy-Fuel (HVOF) thermal spraying process.Preferably the said powder has a particle size from 10 micrometers to 60micrometers. The thermal spraying melts the particles, then atomizesthem and sprays them onto the substrate at high velocities, quenching onthe substrate and providing an amorphous coating. Another layer wasapplied, using the same process, and bonded with the previous layer.

Example 8

The powder comprising the Ni based amorphous alloy 2 is applied to asubstrate by a High Velocity Oxy-Fuel (HVOF) thermal spraying process.Preferably the said powder has a particle size from 10 micrometers to 60micrometers. The thermal spraying melts the particles, then atomizesthem and sprays them onto the substrate at high velocities, quenching onthe substrate and providing an amorphous coating. Another layer wasapplied, using the same process, and bonded with the previous layer.

Example 9

A powder Ni based alloy is applied to a substrate by a High VelocityOxy-Fuel (HVOF) thermal spraying process in the method described inexample 3. Another layer was applied, using the same process, and bondedwith the previous layer.

Example 10

Molten salts are used as a heat transfer fluid in concentrated solarpower systems (CSP). The heat transfer fluid is used in the receiver.The receiver “heats up due to the incoming solar radiation flux andtransmits heat to a heat transfer fluid. This fluid is usually water,air, or molten salt. The heat transfer fluid is then used, directly orindirectly, to run a turbine that produces electricity through agenerator.

However, molten salts are very corrosive and will damage the pipes thatthey run through. Therefore, CSP systems need effective, corrosionresistant materials that will prevent their pipes from being damaged.

To test the efficacy of the coating in corrosion resistance, sampleswith dimensions 20×10×2 mm and from Haynes 230 (Alloy 230) wereprepared. Samples each of coated sample with the three differentcoatings were exposed, along with uncoated Haynes 230 samples. Sampleswere exposed to molten KCl—MgCl₂ in a 68/32 ratio for 300 hours at 750°C. Optical micrographs of representative samples before and afterexposure are shown in FIG. 3 . After the exposure time is finished, thecapsules were flipped vertically to allow the salt mixture to drain fromthe sample surface, and the capsules were cooled in room temperature.The samples were metallographically mounted and polished to examine thecross sections. As expected, the uncoated alloy Haynes 230 specimensexhibited significant intergranular attack. The coated specimens showedno attack on the base alloy Haynes 230 at all. FIG. 4 shows a close-upof the intergranular attack on an uncoated Alloy 230 samples.

The cross sections were also examined with SEM and SEM-EDS and theresults are shown in FIG. 5 -FIG. 6 . EDS maps are not shown for allsamples, only one of each coating type, but maps were taken of allsamples, and the depicted maps are representative.

As expected, the uncoated Alloy 230 samples had significant Cr depletionalong grain boundaries near the surfaces. The coated samples not onlyshowed no Cr depletion in the base metal but exhibited no Cr depletionin the coatings either.

The depth of attack was measured on both uncoated samples (40measurements per sample) based on the SEM-EDS analysis and is shown inFIG. 7 . The median depth of attack is 33 μm for 300 hours.

Example 11

The Fe-based coatings are fully amorphous up to 650° C. and start tocrystallize after it. At 750° C., 87% of the coating was crystallized.The coating still provides the full corrosion resistance that it didwhen it was amorphous. The crystallinity was estimated by the area ratioof the major peaks of the heat-treated samples to that of the coating inas-sprayed conditions.

Example 12

The samples after corrosion testing were tested by using XRD. The X-raypattern of the samples after molten salt testing are consistent with theX-ray diffraction results of heat-treated samples. However, the peaksintensity on the samples that was immersed in molten salt are differentcompared to the heat-treated sample under the same temperature. Thatcould be explained either through different cooling rates of the samplesor through the different holding time. However, in both cases hardphases of chromium boride, chromium carbide, molybdenum boride andternary carbide of ferro-molybdenum were identified in a highconcentrated chromium phase (Cr0.7Fe0.3) matrix. Same observations weredone for the Ni-based coatings.

While the presently disclosed embodiments have been described in detailwith reference to particularly preferred embodiments, those skilled inthe art will appreciate that various modifications may be made theretowithout significantly departing from the spirit and scope of theembodiments.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

The invention claimed is:
 1. A material comprising a compositecomprising an amorphous metal ceramic composite comprising an iron-basedamorphous metal alloy and a ceramic formed from the iron-based amorphousmetal alloy, wherein the composite exhibits a higher corrosionresistance than that of a Haynes 230 alloy when immersed in a moltenchloride salt comprising KCl and MgCl₂ in a ratio of 68/32 for 300 hoursat a temperature of 750° C.; wherein the iron-based amorphous metalalloy is fully amorphous up to 650° C. and starts to crystallize at atemperature higher than 650° C., and the ceramic comprises a boride anda carbide; wherein the iron-based amorphous metal alloy comprisingFe_(100-(a+b+c))(Cr_(a)X_(b)Y_(c)); wherein a is about 10 to 50 wt. %; bis between 0 to 30 wt. %, and c is between 0 to 10 wt. %; wherein X andY are elements, and X is selected from the group consisting ofmolybdenum, copper, cobalt, aluminum, titanium, tungsten, niobium,silicon, vanadium, and combinations thereof, and Y is selected from thegroup consisting of boron, carbon, silicon, and combinations thereof. 2.The material of claim 1, wherein the composite exhibits no corrosionwhen immersed in the molten chloride salt at the temperature of 750° C.3. The material of claim 1, wherein the composite is formed from theiron-based amorphous metal alloy within 300 hours of exposing theiron-based amorphous metal alloy above 650° C.
 4. The material of claim1, wherein the composite is not fully amorphous or at least partiallycrystalline.
 5. The material of claim 1, wherein the amorphous metalceramic composite is configured to be a component of a solarconcentrator.
 6. The material of claim 5, wherein the componentcomprises a lens or a mirror.
 7. The material of claim 1, wherein thecomposite exhibits substantially no corrosion when immersed in themolten chloride salt for at least 300 hours.
 8. The material of claim 1,wherein the composite comprises a coating.
 9. The material of claim 1,wherein the iron-based amorphous metal alloy comprisingFe_(100-(a+b+c))(Cr_(a)X_(b)Y_(c)); wherein a is about 10 to 50 wt. %; bis greater than 10 to 30 wt. %, and c is between 0 to 10 wt. %; whereinthe iron-based amorphous alloy comprises B, C and Si in a range of about0 to about 10% by weight in total.
 10. The material of claim 1, whereinthe amorphous metal ceramic composite is in form of particles with aparticle size ranging from about 10 μm to about 60 μm.
 11. A materialcomprising a composite comprising an amorphous metal ceramic compositecomprising a nickel-based amorphous metal alloy and a ceramic formedfrom the nickel-based amorphous metal alloy, wherein the compositeexhibits a higher corrosion resistance than that of a Haynes 230 alloywhen immersed in a molten chloride salt comprising KCl and MgCl₂ in aratio of 68/32 at a temperature of 750° C., wherein the nickel-basedamorphous metal alloy is fully amorphous up to 600° C. and starts tocrystallize at a temperature higher than 600° C.; and the ceramiccomprises a boride and a carbide.
 12. The material of claim 11, whereinthe nickel-based amorphous metal alloy comprisingNi_(100-(a+b+c))(Cr_(a)X_(b)Y_(c)); wherein a is about 10 to 50 wt. %; bis between 0 to 30 wt. %, and c is greater than 0 to 10 wt. %; wherein Xand Y are elements, and X is selected from the group consisting ofmolybdenum, copper, cobalt, aluminum, titanium, tungsten, niobium,silicon, vanadium, and combinations thereof, and Y is selected from thegroup consisting of boron, carbon, silicon, and combinations thereof.13. The material of claim 12, wherein the nickel-based amorphous alloycomprises Mo and C less than 5% by weight in total.
 14. The material ofclaim 12, wherein the nickel-based amorphous alloy comprises B, C and Siin a range of about 0 to about 30% by weight in total.
 15. The materialof claim 11, wherein the nickel-based amorphous metal alloy is in formof particles with a particle size ranging from about 10 μm to about 60μm.
 16. The material of claim 11, wherein the composite comprises acoating.
 17. The material of claim 11, wherein the composite exhibitssubstantially no corrosion when immersed in the molten chloride salt forat least 300 hours.
 18. The material of claim 11, wherein the compositeexhibits no corrosion when immersed in the molten chloride salt at thetemperature of 750° C.
 19. The material of claim 11, wherein thecomposite is formed from the nickel-based amorphous metal alloy within300 hours of exposing the amorphous metal alloy above 600° C.
 20. Thematerial of claim 11, wherein the amorphous metal ceramic composite isconfigured to be a component of a solar concentrator.